1. Field of the Invention
The invention relates to a screwdriver that includes a silent clutch.
2. Description of the Related Art
An electric screwdriver is disclosed in unexamined Japanese laid-open patent publication No. 61-219581. The known screwdriver includes a silent clutch mechanism to connect a tool bit to a motor for transmitting the rotating torque of the motor to the tool bit. The silent clutch includes clutch members with clutch teeth that can be engaged with each other to transmit the motor torque to the tool bit. By utilizing the silent clutch mechanism, when the screw is tightened to a predetermined depth with respect to the work-piece, the clutch members can be promptly disengaged to stop transmission of the rotating torque of the driving motor. As a result, noise and vibration during screw-tightening operation can be avoided.
According to the known screwdriver, it is necessary to assuredly perform the disengagement of the clutch members when the screw-tightening operation is completed in order to prevent the clutch teeth of the clutch members from contacting with each other during the operation. Thus, further improvement of technique is desired to promptly and assuredly disengage the clutch members to cut the transmission of the motor torque in various operating conditions of the screwdriver.